The three victims in the story represent the three basic weaknesses of a man.
The first one – the old man – when tries to help the killer (who identifies himself as M) is not sure of his knowledge about the right path. The uncertain old man here represents “Self-doubt”.
The second one – the pretty girl in the car - underestimates the killer (who identifies himself as A) and tells him outright that he can’t reach his destination. Here, she represents “self-condemnation”.
The last one – the burly man at the graveyard – tries to scare away the killer (who identifies himself as N). He represents the deadliest weakness of a man – “Fear”.
The letters that the killer gives as his name; when added becomes MAN – representing every person in this world, irrespective of gender, race, culture, etc.
In the story, his journey becomes easier with each killing, and his surrounding, which is quite difficult to interpret in the beginning, becomes easier to understand upon killing the people (weaknesses).
A man can attain his true freedom only when he first realizes his weaknesses, and then kills them. This is what is shown in the last paragraph, when the protagonist, before switching off the light catches a glimpse of the book “Freedom at midnight”. Freedom at midnight it is (freedom at last); he says to himself, before drifting of to a peaceful sleep.